High performance nanocomposites were prepared by incorporating 0–12 vol.% nano-sized (39 nm) Al2O3 particles into PEEK matrix using compression molding. The microhardness and dynamic mechanical properties of the nanocomposites increase with increasing Al2O3 content. The wear resistance of the nanocomposites evaluated at a sliding speed of 1.0 m/s and nominal pressure from 0.5 MPa to 1.25 MPa under dry sliding conditions was improved more than threefold at 0.8 vol.% Al2O3 content. However, the wear resistance of the nanocomposites containing above 1.67 vol.% Al2O3 was deteriorated, despite their higher hardness and stiffness as compared to that of nanocomposites containing lower Al2O3 content. The surface roughness of the wear track formed over the countersurface increases with increasing Al2O3 content. The coefficient of friction of nanocomposites was higher than that of pure PEEK. SEM and optical microscopy have shown that wear of pure PEEK occurs by the mechanism of adhesion mainly, whereas of nanocomposites by microploughing and abrasion. Energy dispersive spectrometry (EDS) shows that Fe and alloying elements of countersurface transfer to the wear debris at higher Al2O3 content.